1. Field of the Invention
The present invention relates to a machining center comprising, in addition to a first main spindle, a second main spindle having a long protruding length for providing turning and milling processes to inner bore portions and the like of a work.
2. Description of the Related Art
Japanese Patent Application Laid-Open Publication No. 2004-66430 (patent document 1) discloses an arrangement of a complex five-axis finishing machine, and Japanese Patent Application Laid-Open Publication No. 2001-150256 (patent document 2) discloses a machining center equipped with a turning head disposed separately from a main spindle head.
Further, Japanese Patent Application Laid-Open Publication No. 2004-130423 (patent document 3) discloses a so-called angle head that converts the rotary force of a tool shank to a right-angle force and transmits the same to a tool.
Japanese Patent Application Laid-Open Publication No. 11-114759 (patent document 4) discloses a machine tool having a two-step feed driving system and equipped with a main spindle head for replaceably attaching tools on a leading end of a ram, and Japanese Patent Application Laid-Open Publication No. 2007-966 (patent document 5) discloses a similar type of machine tool.